Emissions of the potent greenhouse gas methane at a Queensland coalmine were likely between three and eight times higher than officially reported, according to UN-backed research that flew aircraft over the site.
Queensland’s open-cut coalmines are known to be a major source of methane and experts are worried that official figures could be a gross underestimation of actual emissions.
The research, part of the UN environment programme’s International Methane Emissions Observatory (IMEO), is thought to be the first time monitoring equipment on aircraft have been used to directly measure a coalmine’s methane emissions.
Two aircraft with different types of monitoring equipment and flying at different altitudes looked for plumes of methane coming from Glencore’s Hail Creek coalmine in the Bowen Basin – a site highlighted in a previous study as a major emitter.
Glencore challenged the results of that research, published in the American Chemical Society (ACS) journal Environmental Science and Technology Letters.
In 2023, the mine reported total emissions of 0.53m tonnes of CO2-equivalent – including methane and other CO2 emissions – to the government’s safeguard mechanism scheme, which covers sites with high emissions.
But data collected by the UN team’s aircraft suggested emissions just from Hail Creek’s escaping methane were likely between 1.5Mt and 4.2 Mt CO2e per year.
Dr Stephen Harris, at the University of New South Wales and UNEP’s IMEO, said the two aircraft carried different types of methane monitoring equipment but yielded similar results, “increasing confidence in our results”.
“The results suggest this open-cut coalmine, previously identified by satellites as one of the Bowen Basin’s higher emitters, is releasing methane at higher rates than official estimates based on widely used emission factors in Queensland.
“This tells us that more advanced, mine-specific inventory methods – verified by atmospheric measurements – are needed at this facility.”
Levels of methane in the atmosphere have more than doubled since preindustrial times, contributing about 0.5C of the global heating measured so far. The gas has been rising at a record pace in recent years and two-thirds of emissions are human-caused.
Methane is about 80 times more potent than carbon dioxide over a 20-year period at warming the planet. Cutting these emissions is seen as a quick way to slow global heating.
Australia is one of 159 countries to have signed a pledge to cut methane emissions by 30% in the decade to 2030.
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The Albanese government is reviewing how miners calculate the amounts of methane released as they dig for coal. Large emitters have been asked to move from using industry-wide estimates to direct measurements.
But the Climate Change Authority and others are concerned the current framework for using direct measurements – known as “method 2” – is out of date and could also underestimate emissions.
An expert group chaired by the former chief scientist, Cathy Foley, which has been given the UN-led study to review, is examining the methodology.
A report last year from RepuTex, an energy and carbon market modelling consultancy, said as mines moved to method 2 there would probably be a fall in methane emissions reported until the framework was tightened to address integrity concerns.
A spokesperson for the climate change and energy minister, Chris Bowen, said: “The Albanese government has taken strong action to improve methane measurement and continues to progress opportunities identified by the Climate Change Authority in their review of the scheme.”
Glencore said in a statement it had “significant doubts” about the research, claiming it used “out of date” data with aerial surveys over a period representing “less than 1% of the mine’s operating period over a two-year period”.
The company said it had moved to “method 2” of measuring emissions at Hail Creek last year and all it’s Australian coalmines were now using this method. The study did not reflect “inherent mining variability” or emissions upwind of the mine.
“We believe these deficiencies in the paper published by ACS highlight again the shortfalls of satellite/remote sensing methods and unsuitability for annual inventory reporting,” the statement said.
The company was investigating ways “to abate fugitive emissions feasibly and practicably at our open cut mines,” the statement added.
